The present invention relates to a low cost system for the fabrication of storage containers and the containers so formed.
Storage containers or vessels are usually fabricated from cast materials whether metal or plastic or they may be flexible containers with or without reinforcing. The following prior art is believed relevant to the present disclosure. U.S. Pat. Nos. 3,657,042; 4,277,688; 3,875,723; 4,353,763, 4,132,050; 4,409,776; 2,260,064; 4,451,739; European Patent No. 0072429; and my earlier issued U.S. Pat. Nos. 5,022,555 and 5,065,890.
There is a need for a vessel, container, tank or related structure that has low cost, ease of on site fabrication and particularly, a highly custom tailored construction to match demanding specifications.
Broadly, the invention is directed to structural improvements of the containers disclosed in my above-referenced patents, which patents are incorporated by reference in their entireties into this disclosure.
An object of the invention is fabricating vessels with a wide range of dimensions. The vessels may be small enough to accomodate as little as 50 gallons of water (or liquid) when used as a storage container or as large as a unit of which could be 65 feet high with a cross-section of 20 feet by 20 feet when it is utilized as a vessel to hold land fill wastes.
When the vessel is used to support wastes they are digested or decomposed by mixing the wastes with a microbial "soup" under either aerobic or anaerobic conditions to accelerate the decomposition process. Not only will the wastes be greatly reduced in volume but the waste will generate methane gas which can be used as fuel. The vessel is constructed with a heavy liner so that there will be no leakage. The top can be covered with a removable roof with an outlet to draw off effluent gases and odors.
In a preferred embodiment the digestive vessels will be part of a digester farm containing a multiple number of digesters. Typically, the digesters will be in various decomposition modes.
Generally the invention comprises hollow structural members which are joined together by hollow fittings. These members form a frame. When the frame is assembled with the hollow members and fittings, a hollow network of interconnected passageways is formed.
The members are secured to the fasteners by adhesives which either can be a mechanical adhesion or a chemical adhesion, such as cross-linking by polymerization. One can pick from a variety of thermoplastic, thermosetting resins to effect the bond.
This network of hollow passageways is filled with a material which will `set` after filling, thus defining a soldified network which in combination with the members forms a frame of superior strength and rigidity. Received within the frame is a water impermeable liner, such as a plastic liner, to form a seamless vessel. The liner can extend over the top edge of the frame and downwardly over the outside of the frame. The outside of the frame is wrapped with a film material, such as stretch wrap or similar material, or simply bound with tape, such as a polypropylene tape.
In a preferred embodiment of the invention, where the vessel is used to store potable water, a specially designed cover is utilized to provide access to the vessel for introducing water into the vessel while minimizing evaporation from the vessel. Additionally, the frame of the cover is advantageously used.
Hardener filler materials include polymers, such as phenolics, urea-formaldehyde, styrene, styrene copolymers, acrylics, urethanes, vinyls, foams made from resins and polymers, aerated cement, concrete, wood flour mixes, synthetic or natural rubber, latex, molten sulphur, mixtures of rubber or rubber modified products with sulphur or other vulcanizing agents to create a group of strong and resilient cores in the network. Alternatively, a rubber can be extruded directly inside the pipe to form a so-called high durometer rubber product, making for an extremely resilient and strong plastic-rubber combination.
In a particularly preferred embodiment, reinforcing rods, such as Re-bars, steel or poltruded glass fiber bundles, are placed in the hollow network and then the settable material is poured into the passageways to improve the tensile and compressive strength of the frame.
Although in the preferred embodiment standard hollow cylindrical pipes will be connected by standard hollow fasteners, elbows, T-joints, etc., any hollow member can be used. These extruded members can be in any geometric configuration as long as they are hollow and function in combination with the other members to provide a member of increased strength. Other extruded profiles could include I-beams, T-beams, L-shaped structures, etc.
In a particularly preferred embodiment, in lieu of or in combination with standard hollow cylindrical pipes, the pipe is extruded such that the interior and/or exterior of the pipe is extruded in a profile such that the pipe has longitudinal grooves on its surface. These grooves greatly increased surface area over that of a smooth walled pipe so that when stress is applied it is more uniformly distributed thus increasing the resistance to compression/tension failure. When the hardener filler materials are introduced into the network in this type of configuration the greater surface area of the peaks and valleys of the grooves allows the introduction of more hardener material to create additional strength. Correspondingly, the fittings are extruded to mate with the grooved pipe.
Co-extruded members are also advantageous. For example, a member co-extruded with a PVC exterior shell could have a concentric high-impact styrene interior wall treated to have compatible adhesion surfaces. Co-extruded combinations form members with greatly improved resiliency and tensile/compression characteristics while benefitting from cost reductions. An exterior wall could be a resin with good temperature resistance properties and the inner wall a low cost filler resin.
Preferred extruded members include polyvinyl chloride, acrylonitrile-butadylene-styrene copolymers (ABS), polystyrene, polypropylene and glass reinforced fiberglass, metal pipe and tubing such as steel and aluminum. Also suitable are pipes made from paper/board and adhesives, resins and various plies of paper/board. They are typically referred to as "paper cores". Because of their simplicity and manufacturing they are wound to any inside and outside diameters very easily. Thus, they can be tailored to fit standard plastic pipe fittings. The strength of the paper cores can be altered by customizing the resinous/adhesive binders as it is being wound. The exterior can be coated to make it weatherproof and waterproof.